Bokine teialkyl amines



B TRIALKYL AMINES Herbert C. Brown, West Lafayette, Ind., assignor to Ethyl Corporation, New York, N. 2. a corporation of Delaware No Drawing. Application October 7, 1953 Serial No. 384,759

8 Claims. (Cl. 260-583) 'The present invention relates to novel borine-alkyl amine addition compounds. In particular my invention relates to borine-trialkylamine addition compounds whose characteristics are such as to endow them with a number of varied utilities.

Addition compounds wherein an atom of one molecule contributes a pair of electrons for bond formation to an atom of another molecule are known to the art. An example of this type of coordinate linkage is the addition compound resulting from thedonation of a pairof electrons by the nitrogen of an amine molecule to the boron of a borine compound. A number of such compounds have been prepared in the past. However, their utilities have been limited due to their instability and other unfavorable properties.

Certain boron-containing compounds have been suggested as ignition improvers in compression ignition engines. However, the compounds proposed in the prior art have a number of shortcomings. Some of them decompose too readily causing the fuel to flash at too low a temperature. Others are unstable in the presence of water and since commercial diesel fuel almostuniversally contains minor amounts of water, this instability result-s both in reduced ignition quality of the fuel and the formation of troublesome sediments, sludges and the like. Other potential ignition accelerators are colored and thus impart an undesirable coloration to the fuel to which they have been added even when employed in very low concentrations. Since the color of the fuel is generally used by the consumer as a.crite,rion of its quality, it. is .highly desirable that the additive be colorless. Other boron-containing compounds are unstable in the presence of atmospheric oxygen and present a storage problem. Still other compounds are solids and therefore difficult to blend with the fuel. An ideal diesel fuel cetane improver should have the following properties:

(1) The additive should be readily soluble in all types of diesel fuel.

(2) Theadditive should be compatible with high sulfur fuels.

. (3) The additive should be equallycffective in both straightrun and catalytically cracked fuels.

1 (4) The additive should have a boiling point not above that of the diesel fuelitself to prevent evaporation 1osses on. storage.

(5) The additive should not materially reduce the flash point of the fuel in question.

(6) The viscosity and pour point of the additive should be such that no difficulty is experienced in blending procedures, regardless of temperature conditions.

(7) The additive should be non-hazardous to both personnel and equipment.

It is evident, therefore, that the state of the art would be greatly enhanced by a class of borine amine addition compounds which accelerate ignition due the energy liberated upon the rupture of the boron to nitrogen bond and subsequent reaction of borine with oxygen at the elevated temperature of the combustion chamber, and

States Patent 2,860,167 Patented Nov. 11, 1958 2 which would in addition also fulfill the above enumerated requirements.

Consequently, it is an object of the present invention to provide new compositions of matter useful as cetane' improvers for distillate fuels in the diesel fuel boiling range. i i

An additional object is to provide a cetane improver of enhanced stability in the presence of water.

Another object of my invention is to provide a fuel additive which is colorless and thus does not add an 0bjectio-nable color to the fuel mixture. l V 4 it is an additional object to provide a c etane improver which is in a liquid form at ordinary temperaturesand therefore easily blended with fuels.

Another object is to provide an additive which is compatible with different types of fuels. i

Another object is to provide a process for the preparation of the novel compounds of my invention.

Other objects of the present invention will become apparent from the subsequent discussion. i

I have found that the above and otherobjects can be accomplished by practicing my invention which consists of providing as new compositions of matter addition compounds wherein one molecule of borine is bonded to one molecule of a trialkylamine, in which the total number of carbon atoms in the amine varies from four to about twelve. Such compounds may be defined by the general formula i i in which R R and R are ,alkyl groups and can be the same or different and wherein the total numberof carbon atoms represented by R +R +R varies from four to about twelve.

Typical compounds of the present'invention are exemplified by such compounds as .bor i ne dimethylethyI- amine, borine methyldiethylamine, .bQr ine dimethYlQnpropylamine, borine methyldi n propylalnfine, borine -.dimethylisopropylamine, borine methyldiisopropylamine, borine .diethy l nlpropylarnine, borineethyldi n prop lamine, borine diethylisopropylamine, borine ethyldiisopropylamine, borine diethylbutylamine, borine ethyldibutylamine, borine diethyl tbutylamine, borine ethyldi t hutyl amin e, borine diethylamylamine, borine ethyldiarnylarnirie, borinetriethylamine, borine tributylamine, borine dir rlethyL butylamine, borine methyldibutylamine, and various other combinations and permutations of alkyl radicals attached to the nitrogen ,which yields a total number of carbon atoms from four to about twelve. i i

The compounds of my invention can be prepared-by passing diborane into a slight erices's' of t he appropriate trialkylarnine which can be contained in a solvent nonreactive toward diborane. The reaction is conducted in an inert atmosphere, such as in nitrogen and the reaction vessel is cooled by means of an i'cesalt bath or some other appropriate method. The addition product is best separated by fractional distillation. Several specific ekamples are given below.

Example I V Borine-triethylamine.-B H was generated by adding dropwise milliliters of B1 etherate (1.06 moles) to 200 milliliters of an ether solution containing 0.65 mole of LiAlH according to the method of I. Shapiro et al., I. A. C. S. 74, 901 (1952). The diborane formed was bubbled into a solution of milliliters (1.3 moles) of purified triethylamine (boiling between 88.5;and'89.0 C.) and 20 milliliters of ether contained under a nitrogen atmosphere. The glass reaction vessel was cooled 3 an ice-water bath. The product was purified by fractional distillation in a vacuum line under a reduced pressure of the magnitude obtainable with a vacuum oil pump. The solution was distilled through a trap cooled with a salt-ice bath into a vessel cooled with liquid nitrogen. .The ether and excess triethylamine were collected in the vessel cooled with liquid nitrogen, while the borine-triethylamine condensed in the salt-ice trap kept at l7 C. The product borine-triethylamine,

H3BZN(C2H5)3 melted at -4 C., forming a colorless liquid and had a vapor pressure of approximately l millimeter at 28 C. The rate of hydrolysis of this compound is very low. Onemilliliter of H B:N(C H allowed to stand in con tact'with 1 milliliter of water for three days produced only 2 milliliters'of non-condensable vapor, which was presumed to be H Example 11 v Boring-tributylamine.--Tributylamine was purified by a distillation at a reduced pressure of about 12.5 millimeters mercury. A fraction boiling at a constant temperature of 90 C. was collected for use in this synthesis. The borine-tributylamine was prepared in a manner similar to the preparation of borine-triethylamine by reacting diborane with tributylamine, with the exception that benzene was used as a'solvent. The reaction was carried out at a temperature of 25 C. in a nitrogenatmosphere. The H B:N(C H was obtained in 84 percent yield based on the amount of BQH bubbled in. v

The product, H B:N(C H had a melting point of -12 C., producing a colorless liquid of a very low vapor pressure. Heating the product to 70 C. at a pressure less than 1 millimeter mercury in a vacuum line did not result in any noticeable distillation to a cold trap.

Example III Borine dimethylethylamine..The borine dimethylethylamine was prepared in a, manner similar to that inside the reaction vessel.- Another means of cooling is on vaporization.

used in the preparation of borine-triethylamine, by r'eacting diborane with dimethvlethvlamine in a nitrogen atmosphere. The product H B:N(CH C H was obtained in 84 percent yield based on the amount of BOHQ bubbled in. The HQB:N(CH C H is a colorless liquid, melting at 17.7 C.

Example IV Borine-diethylmethylamine.-The method of preparation of borine-diethylmethylamine was similar to that used in Example III by reacting diborane with diethylmethylamine in a nitrogen atmosphere. An 86 percent yield of H B:N(CaH )nCI-IQ was obtained. The product melted at 38 to 40 C. yielding a colorless liquid.

While the examples given above illustrate a convenient method for the preparation of the com ounds of my invention,'it will be obvious to one skilled in the art that many variations and modifications are possible in adapting this method for alternate commercial processes. For example, while benzene and diethyl ether were found to be eflicacious solvents in the synthesis of borine-trialkylamines, other solvents may be used. Illustrative examples of ether solvents are dimethyl ether, methylethyl ether, diethyl ether, ethyl-propyl ether, dipropyl ether, ethyl isopropyl' ether, di-isopropyl ether, methylpropyl ether, dibutyl ether, amyl ether, hexyl ether, heptyl ether, octyl ether, dodecyl ether, anisole, phenylethyl ether, phenyl sulfide, and the like. These are but a few examples of the straight chain ethers, branched chain ethers, mixed aliphatic ethers, aromatic-aliphatic ethers in which the aromatic substituent may be alkyl substituted, aliphatic ethers with aromatic substituents,

dioxane and other cyclic ethers, halogenated ethers, the

glycol ethers such as p-ethoxy ethanol. The ethers may thus be either oxy-. or thio-ethers.

' vent, if one is used, can'be distilled off and fed back into Ethers, othe than 76 .der a nitrogen or other inert atmosphere. The product '4 7 those mentioned above will be apparent to those skilled in the art.

Other solvents that may be used are .straight and branched chain aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane, diethyldimethylmethane, triethylmethane, cyclohexane and the like; aromatic and substituted aromatic hydrocarbons such asbenzene, toluene, the xylenes, ethyl benzene, propyl benzene, etc.; halogenated hydrocarbons such as chloroform, ethylene= chloride, methylenebromide, carbon tetrachloride, ethyl"- bromide, propyl bromide, propyl chloride, the dibromo propanes, the dichloropropanes, the butyl, bromides, the chloropentanes, bromobenzene, m-bromochlorobenzene; chlorobenzene, m dichlorobenzene, p dichlorobenzene, 1 etc. Mixtures of various solvents can also be used. An, example of mixed hydrocarbon solvent is a petroleum fraction such as that obtained by a cracking process or other well-known methods. Since it is not desirable to have a high concentration of olefinic material in the solvent, the petroleum fraction can be first subjected-tof a treatment well-known in the art for the reduction of the olefinic content thereof. The above are non-limiting; examples of the various hydrocarbons and halogenated hydrocarbons that may be used as solvents. T

While solvents were employed in the synthesis of the borine-trialkylamine compounds of the present invention, the reactions can be carried out equally Well in the ab-- sence of solvent. a

In the examples given above, the reaction mass was cooled by external means. Other means of cooling can be used. One method would be the use of cooling coils the use of a low boiling solvent whichwould absorb heat I on vaporization. On the other hand, since the tempera-"f ture of the reaction is not critical, the-trialkylamine used in the synthesis may serve as a coolant by absorbing'heat The vaporized substance can be con densed on the cooler parts of the apparatus or with the aid of condensers or equivalent means and returned to the reaction zone. The manufacture of the borine-trialkylamines of the; present invention may be carried out as a batchv orcon-I tinuous process. In a continuous process the diborane and the trialkylamine can be fed continuously into the reaction vessel. When so doing, a portion of the reac" tion mass can be continuously withdrawn and passed through a zone wherein the trialkylamine and the solthe reaction zone while the product, borine-trialkylamirie is drawn off by conventional means.

In synthesizing these compounds one should observe the necessary precautions apparent to those familiar. with the art. For example, since diborane cannot be exposed to air the reactions are preferably conducted unshould be kept away from strong concentrated acid, since the strong acid decomposes the addition compound, forming borine which in turn recombines to' form di borane with the liberation of heat. Hence, in the'pr es ence of air an explosive mixture of oxygen and diboran may result. The above precautions should therefor be taken in spite of the fact that the borine-amine addition compounds of my invention are more stable than alkylborine-trialkylamines. p i

The compounds of my invention are novel and have the unexpected property of being liquids at ordinary? temperatures. For example, borine-dimethylethylamine, H B:N(CH C H melts at 17.7 C., whereas the tri-; methylamine derivative H B:N(CH is a solid melting, at a relatively high temperature of 94 C. It is, there-n fore, unexpected and surprising that the replacement of an ethyl group for one of the methyl radicals on the nitrogen atom lowers the melting point by more than 76 degrees. It is not inconceivable, therefore, that l my compounds possess a type of chemical bonding f or electron configuration different from superficially related addition compounds of the conventional type.

The unexpected property of being in the liquid state at ordinary temperatures makes the compounds of my 6 car, barrel, gallon of smaller lots. The borine-trialyklamines of the present invention can thereforebe stored in tanks, barrels, or in smaller containers depending on the volume of fuel to be blended. After adding the invention useful as solvents. They are especially valuable 5 borine-trialkylamine to the fuel, the liquid is stirred, or" in cases where the dielectric constant of the solvent is agitated by some other means, until a homogeneous a critical factor in a specific operation since the dielecmixture results. Here again the advantages of the trio property of the compounds of my invention may be liquid form of the compounds of my invention are e x. varied and finely adjusted by a suitable choice of the hibited since a liquid is more easily blended .into a alkyl groups attached to the nitrogen. 10 fuel while a solid would tend to settle out and would As agricultural chemicals the borine-trialkylamines of require more drastic methods to bring into solution. .An my invention can be used as fungicides, insecticides, alternative method of blending is to .first dissolve the miticides, herbicides and plant growth regulators, and additive in a small amount of fuel and then adding the as soil conditioners. The compounds in question also cetane improver in the form of a concentrate to the make excellent amine carriers. bulk of the fuel and stirring or agitating until a ho- It was also discovered that the compounds of the mogenous mixture results. present invention are colorless liquids. As indicated, this The. amount of the borine-trialkylamines in the fuel can is an exceptionally good quality in the use of these comvary from 0.01 to about 5 weight percent depending on pounds, particularly when employed as cetane improvers the fuel used and the improvement in the ignition 'qu'ali since it is not desirable to change the color ofa fuel ties desired. For example, it has been found that varyupon admixture therewith of an additive. ing the concentration of the additive in' a straight run Another important property inherent in the compounds fuel from 0.1 to 1.0 weight percent resultsin an increase of my invention is their remarkable stability against in the ignition rating of from about 3.2 to about 15.7 oxidation. Contrary to expectations they do not react cetane numbers. The following examples are illustrative or otherwise deteriorate in the presence of oxygen from of the results obtained. g Y the atmosphere. It would appear, therefore, that this Exam 1 V r p e characteristic of my novel borine-trlalkylarnme compounds further establishes their unusual and peculiar To 1980 Parts by 2i" Stralght Pull diesel fuel, Chemical bonding, which at least in part may explain was added 20 Parts of boflne-triethylamifle and the their unexpected properties and hence utilities. ture was stirred until a homogeneoussolution resulted. Another property the Compounds possess is remark This produced a diesel fuel composition in which the able resistance to hydrolysis. By Way f example borine-triethylamine was present in 1.0 percent by weight; hlhrinetriethyfiimine fwasdleift iiIIZOHtEIiCt withnwater tfor Example VI 7 ree ays an was oun o ie on a sma uan 1t of gas. This is indicative of the extr me resista nce mi To 720 parts by Weight of ig run dlesel fuel" compounds of this invention possess against hydrolytic was added. Parts of comliosmon of Example decomposition notwithstanding other indications of their T blendmg was accomphshed m same fi as relatively low intrarnolecular cohesive forces. Lhe previous example. h resulting solutwn. 0.0m-

All the above properties are essential in a good cetane tamed percent of p i i In a slmllar improven The efiectiveness 0f the compounds of the 40 manner, fuel compos tlonscontam ng 0.2, 0.4 and 0.6 present invention in improving the ignition qualities of Welght percent of ii i were prepared" a diesel fuel is shown by comparison with a standard pmcqdure as Set forth .heremabove was {epeated reference fuel in a C. F. R. engine using the ignition i Catalyncauy t fuel In tf of the i i delay method according to the method described in dlesel fuel to Obtam fliel composmons. confalmng 5 American Society for Testing Materials volume 36 I, 0.2, 0.4, 0.6 and 1.0 weight percent borine-triethylamine 418 (1936) in sa d catalytically cracked fuel. w g

ln blending the cetane improver with the fuel, either Blend? of bonne'dimefliyethylanilme b,onne'm ethyldl' of the straight run or catalytically cracked variety, the eihylamme and borlne-trlbPtylamme wlth stmlght'mn components can be measured out by Weight Having diesel fuel were made up in an analogous manner to weighed a volume of fuel or determined its weight from Prowde fuels With imPmWd ignition qualities for use its volume and a knowledge of its specific gravity, an in Compression ignition enginesappropriate amount of the desired borine-trialkylamine Th table given bel w shows the cetane improvement or a mixture of various borine-trialkylamines f my obtained by an illustrative number of the novel cominvention to be used as an additive can be weighed pounds of my invention.

Increase in Octane Number for Cetane Weight Percent Additive Additive Fuel Numoer B3B 2 N(CH3)202H5 Straight IUJ1 33. 1 4. 3 6. 0 15. 7 H3B:N(C3H5)2CH d0 33. 1 3. 8 6. 2 14. 9 H313:N(I1C4H0)a. d0. 33.1 3.2 4.7 11.4 HaB N(C2H5)a (1D 33.1 3.3 5.3 14.7 H3B:N(C2H )3 Catalytically 25.5 4.0 5.8 12.5

cracked.

or measured.

Since the compounds of my invention are liquids, advantage can be taken of their specific gravities to measure them out by volume in order to obtain the desired amount of the additive. The volume method is usually a much faster means of measurement than weighing and therefore the advantage of the liquid property of the compounds of my invention is herein displayed. The blending can be performed in storage tank, tank Thu-s, it is seen from the above examples that a marked increase in cetane number of compression ignition fuel is obtained by the addition thereto of small amounts 0 of borine-trialkylamine compounds.

Other advantages to be obtained by employing the compounds of the present invention as cetane improvers are increased engine cleanliness, increased storage stability, increased solubility, and the like.

Although my compounds have been shown to be useful improving the cetane rating and other properties of hydrocarbon idols of the diesel fuel boiling range, they can be successfully utilized as additives to other hydrocarbon compositions. For example, minor proportions of these compounds can be blended with burner fuels to improve their combustion characteristics. Likewise, by blending minor proportions of the compounds of my invention with unctuous solvents such as natural and syntheticlubricating oils and greases the characteristics thereof can be materially increased. Similarly, the borine-trialkylamines are effective in improving the combustion characteristics of jet and rocket fuels as well as being especially effective as starting aids for diesel and jetengines. 1

In addition'to the above uses the borine-trialkylamine compounds are valuable as. chemical intermediates. 4 Having fully described the nature of the novel compounds of the present invention, I do not intend that my invention be limited excep-twithin the spirit and scope of the appended claims. I claim:

Eorinetriethylamine having the formula BHatN-CzHs CzHu 2. Borine .tributyl amine. 3. Borine dimethylethyl amine. 4. Borine methyldiethyl amine. 5.,Ay,process for the preparation of borine trialkyl amines wherein one molecule of borine'is bonded to one molecule of a trialkyl amine in which the total number of carbon atoms varies from 4 to about 12; said process comprising reacting at substantially atmospheric pressurefunder cooling, and in the presence of an inert gas and an inert solvent, diborane with a trialkyl amine corresponding to the general formula '7: I N R2 R: wherein R R and R represent alkyl groups and wherein the total number of carbon atoms in the three alkyl groups varies from '4 to about 12. 6. process for the preparation of borine triethyl amine comprising reacting substantially one moleor diborane with substantially 1.3 moles of triethyl amine in ether solution under a nitrogen atmosphere at sub stantially atmospheric pressure with cooling, and rec'over-f ing borine triethyl amine by distillation from the reaction mixture. I r

7. An addition compound wherein one moleculepf borine is bonded to one molecule of a trialkyl amine corresponding to the general formula wherein R R and R represent alkyl groups and wherein '4 i responding to the general formula the total number of carbon atoms in the three'alkyl groups varies-from 4to 12.

8. An addition compound wherein one molecule of borine is bonded to one molecule of a trialkyl amine cor-;

References Cited in the file of this patent UNITED STATES PATENTS 2,234,581 Rosen Mar. 11, 1941 2,257,194 Rosen Sept. 30, 1941 2,266,776 Leurn Dec. 23,1941 2,267,701 Leum Dec. 23, 1941 2,429,883 Johannson Oct. 28, 1947 2,678,949 Banus'et al May 18, 1954 t OTHER REFERENCES v i Krause: Ber., vol. 57, pp. 813-818 (1924).

Wieberg: Zeit. fiir Anorg. u. All. Chemie, vol. 256; H l

Schaefifer et al.: 71, pp. 2143-5.

Brown et al.: pp. 2340-5. 

7. AN ADDITION COMPOUND WHEREIN ONE MOLECULE OF BORINE IS BONDED TO ONE MOLECULE OF A TRIALKYL AMINE CORRESPONDING TO THE GENERAL FORMULA 